1. Field of the Invention
The present invention relates to an illumination light detecting optical system and an optical apparatus and an endoscope apparatus provided with the same, for detecting abnormal illumination light in an illumination optical system in which for example, a fluorescence luminescence component is irradiated by LD light etc. as excitation light, and light which is mixed with the excitation light and fluorescence from the fluorescence luminescence component is used as illumination light.
2. Description of the Related Art
So far, an endoscope has been used for observation of a part which is difficult to observe from the outside in cases such as a medical treatment and/or diagnosis of inside of body of a patient in the field of medicine, an inspection of inside of a pore formed in a product in the field of industry, etc.
Generally, an endoscope has an image transmission optical system, an objective optical system, a relay lens (in case of a rigid endoscope) an image guide fiber (in case of a flexible endoscope) etc., in the inside of an insertion part at a top part having a cylindrical shape with small diameter. And, it is constituted so that light emanated from an observation object and passes through these optical systems may be observed as an observation image through an eyepiece optical system or an image pick-up optical system. In a video endoscope, it is constituted that imaging elements, such as an objective optical system and CCD, are built in at the top part.
In an endoscope, an illuminating means for illuminating an observation object by an objective optical system is arranged.
The illuminating means comprises a light source, a light guide which leads the illuminating light from the light source to a top part of the endoscope.
As the light source in a conventional endoscope apparatus, for illuminating the inside of the space of an object of examination brightly, lamps having comparatively large power consumption (a halogen lamp, a xenon lamp, a metal halide lamp) have generally been used. In recent years, in order to aim at reduction of power consumption, semiconductor light emitting element of low power (LED, LD) has been used as a light source.
For example, in an endoscope apparatus using LD for the light source, it is constituted such that excitation light of the predetermined wavelength emanated from LD is irradiated to a fluorescence luminescence component arranged in the top insertion part of the endoscope through a light guiding means which consists of optical fiber, etc., and in a fluorescence luminescence component, white color light converted by mixing excitation light and the excited fluorescence is irradiated to a space of an object to be examined (an examination object space).
By the way, in an endoscope, failure of light source (LD) and the like may happen, and an optical fiber of a light guiding means may be broken. In such state, if it continues using it as it is, light leaks out, and an amount of illumination light irradiated from the top of an insertion-part of the endoscope decreases, and accordingly an object to be examined (an examination object) will become dark. In a conventional endoscope, in order to control an electric power supply to a light source (LD) (for example, the electric power supply to the light source is stopped when an amount of light is small), a constitution equipped with an illumination light detecting means in which a predetermined amount of the illumination light is extracted, and its intensity is detected has been proposed.
The illumination light detecting means shown in Publication of the Japanese unexamined patent application, Toku Kai 2006-158716 is constituted as shown in FIGS. 1 and 2. For example, it is constituted so that light emitted from a side 151a (FIG. 1) of a fluorescence luminescence component 151 arranged to the a top part 150 of an endoscope, and an end surface 151b (FIG. 2) that is at the opposite side to an object to be examined (examination object) is received by light sensors 152 (FIG. 1) and 152 (FIG. 2).
In the FIGS. 1 and 2, a numerical symbol 153 is an illumination light source for lighting LD having a wavelength characteristics for exciting a fluorescence luminescence component 151, a numerical symbol 154 is a light guiding means which leads the light emanated from the illumination light source 153 to the fluorescence luminescence component 152, numerical symbols 155 and 155′ are light guiding means in which light emanated from a side 151a (FIG. 1) of the fluorescence luminescence component 151, and an end face 151b (FIG. 2) that is at an opposite side of an examination object is led to light sensors 152 and 152′, and a numerical symbol 156 is a communication line (illustration is not shown) for sending a signal of the light received by the light sensors 152, and 152 to the optical detecting means.